1. Field of the Invention
The present invention relates to a tire noise reduction device. More specifically, the present invention relates to a tire noise reduction device including a noise absorbing member having an improved performance of resistance to embrittlement under low temperature, the noise absorbing member made of a porous material and arranged on the inner circumferential surface of a tire.
2. Description of the Prior Art
A cause of noises made by a pneumatic tire is cavity resonance sound which occurs due to vibration of the air filled in the tire. The cavity resonance sound occurs when the air filled in the tire vibrates due to vibration caused in a tread part of the tire. This is a result of deformation which occurs in the tread part each time the tread part repeatedly contacts the road surface during rotation of the tire.
As a method of reducing noises which occur due to such a cavity resonance phenomenon, Japanese Patent Application Kokai Publication No. 2004-291855 discloses a tire noise reduction device including an annular noise absorbing member which is made of a porous material and is arranged on the inner circumferential surface of a tire. However, the noise absorbing member which is made of a porous material and is arranged on the inner circumferential surface of the tire has the following problem: the noise absorbing member is damaged by friction of the noise absorbing member with the inner surface of the tire, which is generated by repeated compressive deformation of the tire when the tire is rotating. As in the embodiment described in FIG. 6 of Japanese Patent Application Kokai Publication No. 2004-291855, such a noise absorbing member can be effectively prevented from being damaged by covering the outer circumferential surface of the annular noise absorbing member with a thermoplastic resin film as a protective layer.
Nevertheless, when such an approach is employed in a tire used in a cold weather area, another problem arises. Since the tread in contact with iced and snowed road surfaces is placed under low temperature conditions, the thermoplastic resin film in contact with the inner surface of the tire becomes brittle and broken, and thus stops functioning as the protective layer.